Sound transmitter for gaseous operating fluid



B. 1.. HOLM 3,429,294 SOUND TRANSMITTER FOR GASEOUS OPERATING FLUID Feb. 25, 1969 Filed Aug. 18, 1966 3,429,294 SOUND TRANSMITTER FOR GASEOUS OPERATING FLUID Bengt Lennart Holm, Malmo, Sweden, assignor to Kockums Mekaniska Verkstads Aktiebolag, Malmo, Sweden Filed Aug. 18, 1966, Ser. No. 573,422 Claims priority, application Sweden, Aug. 24, 1965,

11,025/ 65 US. Cl. 116142 Int. Cl. Gilli; 9/22, 9/02, /00

1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to sound transmitters for gaseous operating fluid, the movable part of which is a circular diaphragm provided in a housing and held by its inherent elasticity in engagement with an annular, preferably circular seat concentric with the periphery of the diaphragm to form a valve member controlling the communication between an inlet passage outside the seat and a resonator passage within said seat. In such sound transmitters, when operating fluid, usually air or steam, is supplied under pressure to the inlet passage, the diaphragm is raised from the seat as soon as said pressure has attained a value enabling it to overcome the force by which the diaphragm is held in engagement with the seat. A pressure shock will arise in the resonator passage, and according to generally known principles this pressure shock in turn results in several successive pressure shocks of a frequency substantially determined by the acoustic conditions in a horn connected to the resonator passage.

The diaphragm may be secured at its periphery in many diflerent ways in the housing. Frequently, the diaphragm is fixedly clamped at its periphery by means of a cover provided on said housing and arching over the diaphragm on that side thereof which is opposite the inlet and resonator passages, a planar edge of said cover engaging the edge portion of the diaphragm and urging said edge portion against a shoulder or packing in the housing. A disadvantage of this arrangement is that during the sound production the peripheral parts of the diaphragm cannot move radially during the bulging movements of the diaphragm. Especially if the operating fluid is steam, a fixed clamping of the diaphragm in this manner may result in an undesirable blocking of the diaphragm in bulging position due to radial thermal stresses, unless the diaphragm and the housing always have the same temperature.

A diaphragm which is radially movable at its periphery can be obtained by not clamping the cover against the housing and instead holding the diaphragm in correct position with a certain clearance. However, in most cases this does not bring the desired seal and also results in a not unimportant wear at the periphery of the diaphragm due to the diaphragm movements, for which reason frequent adjustments of the clearance have been necessary.

Finally, the diaphragm can also be secured resiliently, for instance by means of a rubber packing between the diaphragm and the housing or between the diaphragm and the cover, or both. However, if an elastomer is used, there is a certain risk that the characteristics of the elas- States Patent "ice tomer may gradually change, especially when exposed to high temperatures, for instance when the operating fluid is steam.

The present invention relates to a sound transmitter of the type described above, in which the diaphragm is clamped at its periphery against a resilient abutment by means of a cover, but where the drawbacks of present attachment methods are eliminated.

According to the invention, such a sound transmitter is characterized in that the cover abuts one side of the diaphragm along a line located radially inwardly of the general line, located on the other side of said diaphragm, of maximum pressure exerted by the resilient abutment on the diaphragm.

To illustrate the invention and the advantages gained thereby, a number of embodiments will be described in the following, reference being had to the accompanying drawing in which:

FIG. 1 is a partial axial section of a sound transmitter according to the invention, where the resilient abutment is an O-ring;

FIG. 2 is a corresponding section of a sound transmitter where the resilient abutment is a metallic annular member.

The sound transmitter shown in FIG. 1 comprises a housing 10 with a cover 11 and a circular seat 12 fixedly connected with the housing. Between the cover 11 and a packing ring 13 which is of resilient material and rests on a shoulder 14 in the housing 10, there is resiliently clamped a circular diaphragm 15 which is concentric with the seat 12 and by its inherent elasticity is held in engagement therewith so as to form, in known manner, a valve member controlling the communication between an inlet passage or chamber 16 outside the seat in the housing and a resonator passage or chamber 17 within the seat in the housing, the inlet passage communicating with a conduit for the supply of gaseous operating fluid and the resonator passage being connected to a horn. The function of such sound transmitters is well known so that no detailed description would here seem necessary.

In the sound transmitter illustrated in the drawing, the diaphragm 15 is secured in the housing 10 in a manner specific to the invention. Thus, the cover 11 is formed on its inner side with a relatively sharp-edged ridge 18 by which the cover engages the diaphragm along the periphery thereof at a radial distance from the centre of the diaphragm which is smaller than the radial dis tance of that general line along the periphery of the diaphragm along which the packing ring 1'3 in the form of an O-ring exerts its maximum pressure on the diaphragm on that side of the diaphragm which is opposite the cover, the radial position of said line being indicated in FIG. 1 by a dash-and-dot line 19. The attachment of the diaphragm 15 causes adjacent the periphery of the diaphragm a bending moment tending to increase the pressure force of the diaphragm against the seat 12 and having a value which is determined inter alia by the mutual radial distance between the line along which the diaphragm bears against the ridge 18 of the cover and the general line along which the O-ring exerts its maximum pressure on the diaphragm. The bending moment is highly important to the function of the diaphragm and above all to its strength. It is well known that the highest stress of a bulging diaphragm of uniform thickness occurs in the vicinity of the diaphragm centre if the diaphragm is loosely placed along its periphery, i.e. forms a single bulge, while the highest stress on a corresponding diaphragm fixedly clamped in planar position at its periphery, is located in a zone along the periphery adjacent the point of attachment of the diaphragm. However, the most favourable stress distribution is obtained in a resiliently clamped diaphragm where there is a certain bending moment along the periphery thereof.

Considerable advantages are achieved by the invention. First of all, the peripheral bending moment acting on the diaphragm can be mastered in a manner which has hitherto not been possible with resiliently clamped diaphragms, viz. by a suitable choice of the radial distance between the pressure line 19 of the packing ring 13 on one side of the diaphragm and the pressure line of the ridge 18 on the opposite side of said diaphragm. Because the bending moment on the diaphragm is produced according to the invention by means of a force couple adjacent the periphery of the diaphragm, the compression of the packing ring may be relatively insignificant, while still providing an adequate bending moment suitable for the function. In addition, this moment is only slightly dependent on the hardness of the packing so that a change in the hardness due to a possible aging of the material in the packing ring will not deteriorate the function of the sound transmitter. Finally, the bending moment can be favourably influenced by the pressure of the operating fluid in the inlet passage 16. If the resilient abutment is a massive O-ring, as in FIG. 1, or an equivalent metallic O-ring of hollow circular cross sec tion, the ring will be deformed under the action of the pressure, the cross section becoming somewhat higher in the transverse direction of the diaphragm when the pressure in the inlet passage is high so that the line 19 of the maximum pressure of the O-ring against the diaphragm is slightly displaced towards the periphery of the diaphragm 15, and at the same time this pressure increases. Both of these phenomena entail that the bending moment on the diaphragm will be higher; in other words, the pressure of the diaphragm against the seat will be correspondingly higher.

This control function, directly dependent on the pressure of the operating fluid, of the resilient attachment of the present invention is extremely valuable in actual operation. Thus, the sound transmitter can be supplied under a pressure which may vary within relatively wide limits without considerable variations in the intensity of the sound and thus in the consumption of gaseous operating fluid. This is especially important in steam-operated sound transmitters where water of condensation in the steam supply pipe to the inlet passage 16 may often result in an irregular temporary throttling of the supply of dry steam to the sound transmitter; in steamoperated sound transmitters it is ditficult completely to avoid the formation of water of condensation. Thanks to the above mentioned very rapid control through the pressure action on the O-ring 13, the resulting pressure variations in the inlet passage will have no noticeable effect on the sound produced in the sound transmitter, a variation in the pressure of the inlet passage being compensated for by variation of the force by which the diaphragm engages the seat 12.

The design of the resilient abutment can be modified without jeopardizing the considerable advantages described above. Thus, the abutment may be in the form of a metal ring 13' of S or C profile, as is shown in FIG. 2, the said ring being supported in the housing 10 against the shoulder 14 with its one edge and engaging the diaphragm 14 with its other edge.

What we claim and desire to secure by Letters Patent is:

1. A pressure fluid operated sound generator comprising in combination:

(a) a generally cylindrical, horn-like composite housing (b) said housing (10) including annular wall means defining a central resonator passage (17) and terminating at an inner end in unitarily formed annular seat means (12) spaced radially inwardly of said housing wall (10) which latter space constitutes part of a fluid inlet chamber (16);

(c) an elastic diaphragm disk (15) in said housing and having a first and a second face on opposite sides thereof;

(d) rigid annular abutment means (18) connected to said housing and contacting said first face for biasing said second face of said diaphragm disk sealingly against said annular seat means (12);

(e) said annular abutment means (18) contacting said diaphragm disk (15 concentrically with and radially outwardly of said annular seat means (T2);

(f) said diaphragm disk (15) defining together with said housing and said annular seat means (12) an annular inlet chamber (16) for receiving gaseous operating pressure fluid around said annular seat means (12) and said disk further serving as a vibratory valve therewith for periodically admitting pressure fluid from the inlet chamber (16) into the resonator passage (17);

' g) an annular shoulder (14) formed in said housing at the outer periphery of the inlet chamber (16); and

(h) a resilient sealing ring (13) sealingly clamped between said shoulder (14) and said second face of said diaphragm disk ('15) to be directly exposed to the pressure fluid in the inlet chamber ('16) on one side only;

(i) said sealing ring (13) being of and contacting said disk (15) at a greater diameter than said annular abutment means (12);

(j) said resilient ring (13) having a cross sectional shape capable of resilient deformation responsive to the application of pressure fluid in the inlet chamber (16) acting on one side only of said ring (13); and

(k) said ring (13) assumes a greater cross-sectional dimension between said shoulder (14) and said diaphragm disk (15) at increasing fluid pressure in the inlet chamber ('16), whereby said ring (13) aids said abutment means (18) in biasing said diaphragm disk (15) against said annular seat means (12) with an increasing force at increasing fluid pressure in the inlet chamber.

References Cited UNITED STATES PATENTS 1,029,521 6/1912 Weiss 116-142 2,273,968 2/1942 Lewis 116-142 2,352,467 6/ 1944 Broden 116142 2,579,784 12/1951 Broden 116-142 2,65 8,470 11/ 1953 Swanson 1-16--142 2,884,892 5/1959 Swanson 1l6142 3,117,552 1/1964 Swanson 1'16-142 1,085,354 1/1914 Mukautz.

LOUIS J. CAPOZI, Primary Examiner. 

